In applicant's prior U.S. Pat. No. 4,457,509 dated Jul. 3, 1984 and entitled "LEVITATIONARIUM FOR AIR FLOTATION OF HUMANS" there is described an installation to levitate human beings including a specifically designed building wherein the upward flow, upon reaching the top of the building, is caused to return through an annular air passage to the underside of the air propeller so that the air circulates in a closed circuit. Such a building is necessarily expensive to build together with the accompanying air propelling installation and, moreover, it cannot be moved from one site to another. Moreover several users levitated at the same time often hit themselves and may suddenly drop on the safety net above the air propeller, sometimes resulting in injuries.